An electric field is a vector quantity of electric potential gradient at a point in space, and may be measured in unit of volts per meter. Electric field can be generated in various ways such as by a presence of charged particles and movement of the charged particles. Electric field can be measured in various ways. For example, two parallel conducting plates, e.g., a parallel plate capacitor, can be used to measure a local electric field strength. As another example, sensors based on silver/silver chloride electrodes can be used to measure the local electric field strength.
An Electro-Optic (EO) material is material that changes an optical property, such as refractive index and/or absorption coefficient, in response to a local electric field. Some EO materials exhibit a proportional (e.g., linear) change in refractive index as a function of the local electric field, at least over a range of electric field strengths. Examples of such EO materials include Lithium Niobate.